“Your victims were vulnerable. You pose a sufficiently significant risk to children to merit a lengthy sentence.”

Smart met his victims at the City Mission, and their unsuspecting parents believed he was a devout Christian and let him take the youngsters to playparks and swimming pools.

Instead, Smart, of Christian Crescent, Edinburgh, used the time to carry out the abuse.

The mum of the two boys he targeted said: “It didn’t cross my mind that anything like that would be happening.

“If you thought something like that would was going to happen, you would not put them in that position. You trust someone.”

The shocked mother only began to suspect what had happened a decade after the abuse.

She added: “They didn’t want me to find out anything. I was never keen on talking to the boys about sexual stuff.”

Smart’s female victim said he had targeted her after she went into her room for Bible study. He preyed on her for five years from her eighth birthday.

Her medical records showed she had been abused and suspicions about Smart, a Tory candidate in 2003 who also stood for the Democratic Unionist Party, led to his arrest.

The pervert had denied attacking the children and claimed that he had “no sex drive whatsoever” and was impotent.

He insisted he had suffered from the problem for a long time and he had been forced to break off his engagement to a woman because of it.

The former ScotRail train conductor admitted seeing his GP about being impotent within weeks of being told about the child abuse allegations, but he denied that the problem had only started in middle age.

He claimed he didn’t know why the three victims had made the allegations against him and he had been “totally shocked” when he was arrested by police.

Smart, who has led anti- homosexuality demonstrations, claimed he had been targeted because he was so outspoken against such lifestyle choices.

Solicitor advocate John Keenan, defending, said that Smart, a first offender, continued to protest his innocence.